Why do small changes in Earth's temperature have a big impact?

Weather is a complex phenomenon. While we've created sophisticated computer models to analyze and predict weather patterns, we're still learning the intricacies of weather patterns and cycles. For example, the phenomenon of El Niño is particularly complicated.

El Niño is a weather cycle that appears every few years. During a year without El Niño, trade winds typically blow westward across the Pacific Ocean. As the winds travel, they push warm water at the surface of the ocean to the west. Back east, toward South America, cool water from the deeper levels of the ocean rises to the surface. The cooler water is richer in nutrients than warm water. The nutrients help support marine life and play a vital role in the fisheries off the coast of South America.

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During an El Niño event, these trade winds weaken. The warm water at the surface of the eastern side of the Pacific stays where it is, preventing the cooler water from rising to the surface. That means the marine life that depends upon the nutrients that normally rise up suffers.

It also means that weather patterns change. Rain develops as water evaporates from the warmer parts of the ocean. The trade winds in a normal year push the rain toward the west, so that part of the Pacific gets rain while the eastern region remains relatively dry. But during El Niño, the temperature of the surface water doesn't vary as much. Rain can form in the eastern Pacific, causing flooding in South America.

While El Niño is a cyclical event, as temperatures increase, the effects we see during El Niño could become more common. The change in weather patterns could in turn drastically alter everything from marine life to crop cycles on land.

Another potential effect is that global warming could lead to more frequent and stronger hurricanes. We still don't fully understand the relationship between water temperature and hurricane frequency and intensity. Climatologists debate whether warmer oceans will lead to a more intense hurricane season. So while it's possible global warming could lead to stronger hurricanes, we don't have enough data to be sure of that outcome.

It's also important to remember that when we talk about global warming, we focus on a rise in the mean temperature of an area. The mean is the average temperature. So while a couple of degrees seems like no big deal, it also means that the region can experience more extreme weather events like heat waves. An area that might typically experience heat waves 75 days out of the year may see 90 or more after warming just a couple of degrees. That makes a big impact.

Learn more about global warming, its impact on us and the world around us and what we can do about it by following the links on the next page.